It has been acknowledged that females exhibit more smiling behaviors than males, but there has been little attention to this gender difference in the courtroom. Although both male and female witnesses exhibit smiling behaviors, there has been no research examining the subsequent effect of gender and smiling on witness credibility. This study used naturalistic observation to examine smiling behaviors and credibility in actual witnesses testifying in court. Raters assessed the smiling behaviors and credibility (as measured by the Witness Credibility Scale) of 32 male and female witnesses testifying in trials in a mid‐sized Southern city. “Credibility raters” rated the perceived likeability, trustworthiness, confidence, knowledge, and overall credibility of the witnesses using the Witness Credibility Scale. “Smile raters” noted smiling frequency and types, including speaking/expressive and listening/receptive smiles. Gender was found to affect perceived trustworthiness ratings, in which male witnesses were seen as more trustworthy than female witnesses. No significant differences were found in the smiling frequency for male and female witnesses. However, the presence of smiling was found to contribute to perceived likeability of a witness. Smiling female witnesses were found to be more likeable than smiling male and non‐smiling female witnesses. Copyright © 2014 John Wiley & Sons, Ltd.